Modelling the Relationships Between Headway and Speed in Saturation Flow of Signalised Intersections

The headways between vehicles in the traffic flow of intersections are one of the crucial variables for reasonable signal timing setting and intersection configuration design. Many studies apply constant discharge headways to calculate the saturation flow rate, and scarce studies quantitatively investigate the relationship of headway and speed in the saturation flow. This study endeavours to model the headway–speed relationships of saturation traffic flow at the signalised intersection. Five typical intersections with large traffic demand in Golden Coast City are surveyed to collect data regarding vehicles’ discharging speed and headways. The least squared method and the fitting degree test are applied to model the headway–speed relationships at the signalised intersections and compare the models’ fitting performance. The results indicate that the headway is significantly associated with speed. The headway increases with decreasing speed crossing the intersections. The empirically and quantitatively calibrated relationships between speed and headway can be used to calculate the saturation flow rate in the intersections with different discharging speeds and further support the design of intersections with large traffic demand